Thermal relay



l l 1,642,039 Sept. 13, 1927- H, D, MATTHEWS THERMAL RELAY Fild Aprii; 28. 1925 Patented sept. 13, 19.27.

l y 'l '1,642,039 PATENT OFFICE.

HOWARD D. MATTHEWS, or MANSFIELD, omo, A'ssIGNoR To wnsTINGHoUsE ELEC- TRIc a MANUFACTURING ooMPANY, A CORPORATION or PENNSYLVANIA,

THERMAL RELAY.

Application filed April 2,8, 1925. Serial No. 26,333.

My invention relates to thermal protecive means and particularly to thermal re- 3(Snc object of my invention is to provide a relativelysimple and compact thermal relay that shall embody means for effectmg a variable time delay of operation of the device in accordance with the voltage of an energy translating` device with which it is operatively associated. Another ob 'ect of my invention is to prol vide a thermal relay that shall permit of being' employed with any one of a number of energy translating devices having thesame 5 current capacity but different voltage capacities.

In practicing my invention, I provide a pair of cooperating contact members so mounted that `they are respectively actuated 2 by bimetallic, current-traversed elements. One of these bimetallic elements is connected in series circuit relation to the energy translating device and the other bimetallie element is connected in shunt circuit relation thereto. Restraining means is .provided for each of said bimetallic elements, andtheassembly is mounted in a suitable.casing. In the single sheet of drawings, Figure lis a view, partially in sectlon and artiallyin side elevation, of adevice emf odying myinvention,

Fig. 2 is a artial sectional view thereof, taken on the 11ne II-II of Fig. 1,

Fig. 3 is a partial-sectional view therethrough, taken 'on the line III-III of Fig. 1, 4- v Fig. 4 is a dia am of4 connections em'- ployed with the evice embodymg my 1nvention, l 0 Fig. 5 is a schematic diagram illustrating the relative positions of the contact members under various operatingv conditions,

Fig. 6 is a diagram illustrating the heating curves of two different sizes -of energy translating devices, and Fig. 7 is a diagramillustrating the eiective heating curves of the device, forl two',

conditions of operation. y

A thermal relay 11 comprises a 'lower casing 12 and an upper casing 13, that are ofv suitable size and construction to support and receive therein shafts 14 and 15 that may be located in substantially vertical'position and that are preferably located coaxlally. Lower bearing members 16` and.17 and upper bear- 1 gram ofconnections employed with the deing members 18 and 19 are provided forithe two shafts and are of anysuitable construction usually employed in the art.

The shaft 14 has mounted thereon a bimetallic element 21 of relatively heavy crosssection and of spiral form. The inner end of the ymember 21 is suitably mounted on and secured against the-shaft 14, and the outer end thereof is secured against a lug member 22 supported by the casing 12'or by a member mounted therein. For pur oses of adjustment, thev member 22 may e provided with an adjusting` means in a manner well known in the art.

The restraining means 23 comprising a spiral wound spring member, has itsinner end secured to the shaft 14 and its outer end securedv against an adjustable lug '24 that is supported by the casing 12. A movable contact arm 25 of substantially L-shape, has one end thereof secured on the shaft 14`and is vof such length that it extends through a 'suitable opening 26 in one side of the casing 12. The shaft 15 in the upper casing 1 3, has mounted thereon a bimetallic member 27 that is of relatively small area in lateral section and is also of spiral form, with its inner end secured against the shaft 15 and its outer end secured against an adjustable' lug 28.

A spring member 29, of substantially -the same form as the member 23, has its Inner end secured against the shaft 15 and its outer end against a suitable stop member not shown. A movable contact arm 31, of sub-v stantially L-shape, has one end thereofv 90 mounted on the shaft 15, an insulatin collar 32 being located therebetween an ex# tends through an opening in the casin 13. The outer end of the member 31 is provlded with, a suitablecontact terminal that is adapted to engage a cooperating contact tervno minal on the arm 25.

Fig. 4.-A of the drawings illustrates a diavice embodying my invention. energy 10 translating -device 33, here illustrated as an electric motor, but which maybe any other electric energy translating device, such as `a 'transformer or generator, isenergized from suitable supply'circuit conductors 34 and 35 105 through a circuit controlling means 36, here shown asa two-pole circuit interruptor. 4The circuit interrupter36` is provided'with an actuating coil 37, that is adapted, when energi'zed, to attract a core member 38 opera- 11 end of the spirally current capacity,

tively connected to the mechanism of the circuit interrupter to interrupt the circuit through the energy translating deviceF 33. An adjustable resistor 39 is provided that is connected in series circuit relation with the spirally wound volta e thermal element 27, in orderto permit o adjusting the current strength traversing Vthe element 27 The outer end of the bimetallic member 21 has connected thereto the end of a conductor 41, the other end of which is connected to the supply circuit conductor 34, a conductorl 42 being vprovided to connect not only to the movable contact'arm 25 but also to the inner end of the bimetallic element 21, suitableprovision being made to effect an electrical connection therebetween on the shaft 14.

A conductor 43 has one end thereof connected t0 the supply circuit conductor 35 and. the other end to one terminal of the adjust-l able resistor 39, the other terminal of which is connected by a conductor 44 to the inner wound bimetallic element 27. In order to effect such connection, it may be necessary to provide a collar mem-' ber 45 on the shaft 15 that is insulated from the other portions of the shaft but is in electrical connection with the inner end of the bimetallic member 27. The outer end of the bimetallic member 27 is connected by a conductor 46 to the supply circuit conductor 34. The movable arm 31 is connected by a conductor 47 to one terminal of the actuatingIL coil 37, the other terminal thereof being connected to the supply circuit conductor 35.

Figure 6v if the drawings illustrates the heating curves of two translating devices such as electric motors. Curve 48 is that of a relatively small machine and is here as sumed to be that of a motor adapted to operate on a 110 volt circuit. Curve 49 illus' trates the heating curve of a larger machine, which is assumed to have the same current capacity as the motor having curve 48, but adapted to be operated from or connected to an electric circuit of higher potential, such as 220 to 440 volts, or evenf higher. It is evident that the machine having the same-current capacity but adapted to be operated from a will be larger and will have a larger output for a given speed and. slowly than the smallerE be operated from a c ircuitof relatively low voltage. 'M

The device .embodying my invention hasV been designed` to permit its use on energy translating devices of substantially the same thereby simplifying the adjustment of such a device and also permitting of the manufacturer carrying a smaller number o f such thermal 4relays in stock toy meet the demands of the varying sizes of motors. I i y Fig. 5 of the drawings Aillustrates the-povthe the heating will heat up morev machine adapted to sitions of the respective lever arms25 and 31 when the ythermal relay 11'is connected 'to circuits of different voltages as illustrated in Fig. 4. i

The point 5l illustrates the'position taken by the lever arm 25 when it is traversed by substantially the same current, while the points 52, 53 and 54 indicate the respective positions of the lever arm 31 when the-bimetallic spiral 27 and the resistor 39 are traversed by a current that is substantially in accordance with the voltages indicated in Fig. 5, namely, 110, 220 and 440 volts.

If an energy translating device of relatively small size is traversed by a'nvoverload current for a predetermined length of time,y it will heat up more quickly than will a larger energy-translating device. When the bimetallic spiral 21 is traversed by an excessive current, lthe lever *arm indicated by the point 51, will move toward the opoint 52 and engage, that is, provided thefoverload current continues for a long enou h period of time. The actuating coil 37 wi l thereb be energized and the circuit breaker 36 wil be operated to deenergize the energy translating device 33.

If such a thermal relay is employed for an energy translating device of the same current capacity, but of higher voltage, say 22() volts, the position of the lever arm 31 will be moved farther away from the lever arm 51, say tothe point 53 and it will require a longer time to effect operative engagement between the twolever arms under the in.

fluence ofan overload current traversing the bimetallic spiral 21. If the thermal relay is.

employed with an energy translating device connected to a l440 volt circuit, the arm 31- will move to the position indicated by the two lever arms will finally operatively p oint 54 and itv will require a still longer time to e'ect such operative engagement.

It is assumed, of course, that 'the construction of the cooperating parts of the thermal relay embodying my invention is such the movement ofthe relay arm 25 under the influence of the bimetallic s iralmember 21 is great enough to finally e ect engagement with the contact member on the arm 31.

tain types of motors are traversed by anincreasedv current when the voltage is vreduced at the terminals thereof, and this effects a quicker heating of the motor.

' The arm 31 will move into a position inthat;A

. 'nl Fig. 7 of lthe drawings illustrates whattermediate the points 52 and 51 when` the voltage applied to the energy translating de- `vice is reduced. If the current Value is simultaneously lincreased, the movement of the arm 25 will be hastened and the two arms will operatively engage much soonerr than would otherwise be the case. By proper design and adjustment o'f the springmember 29 relatively to the element 27, it is possiblelto effect engagement of the contact members on the arms 25 and 31 when the voltage on the energy translatin device has been reduced to a predetermine percentage of the normal value.

The device embodying myy invention th'us provides a relatively simple and com act two-part thermal relay comprising one t ermostatic element that is subject to the current traversing an energy translating device and a second thermostatic element that is subjected to the voltage of the energy translating device in order to effect an operation of the device that is in accordance with the amountl of energy being translated -in the energy translating device.

By adjusting the position of the outer ends of the bimetallic spirals 21 and 27, it is possible to obtain any predetermined time elay in the actuation of ythe contact members and substantially the same effect may be obtained by adjusting the resistor. 39 that is connected innseries 'circuit relation with the bimetallic spiral 27. The time delay in the operation of the device will be therefore in substantially direct "accordance with the voltage of an electrlc circuit to which an .energy translating device controlled thereby is connected, particularly so as the operating mechanism vis locate in a casing whereby it is heat-insulated and not-affected by radiation from the outside walls of the cas- Various. modifications and changes may .bel made Without departing from the spirit y shafts, a plurality of cooperating contact members carried by said shafts, a bimetallic yelement associated with one of said shafts for actuating the ,same in laccordance with the current traversing'said energy-translating device, and a secondbimetallic element associated with the second shaft for actuat` in'g the same in accordance with the voltage of said energy translating device.

t 2.' A thermal .relay for controlling an electrictranslating device, comprising a shaft,

.a spring-restraining means therefor, a contact .member mounted on said shaft, a spi# rally-wound bimetallic element having one end li-Xed and the other end secured to said shaft, said lspirally-woun'd element being adapted to actuate ysaid shaft and contact member to a predetermined position in accordance with the voltage of said translatn ing device a second shaft co-axial with said first shaft, a spring-restraining means therefor, a contact member on said second shaft, and a second spirallywound bimetallic-element having one end thereof fixed and the other end secured to said shaft, the second bimetallic element being adapted' to actua-te the second shaft and contact member intol engagement with the contact member mounted on the first-named shaft when .a predetermined value of current. has .trav-- ersed thejtranslating device-for a predeter- 'l 4 ,mined length of time." a

In testimony whereof, I have hereunto subscribed my name this 23rd day of Aprily 1925.` f

t 1Howlin? D. MATTHEWS 

